Current living roof systems seek to replicate a soil-based, in-ground system of plants with multi-layered structures or trays placed on a roof surface. The typical commercially available “Green Roof” systems are designed to replicate a soil-based ecosystem by providing a heavy, complicated series of layers to replicate the water flow and rooting material in natural, ground systems constructed on site or pre-manufactured as a modular tray system. The weight of such systems, on the order of 20-30 lbs or more per square foot, requires the roof beams and rafters to be specially engineered and beefed-up to carry the added weight of a saturated living roof system. Thus, for the most part, they are restricted to use in new, specially designed construction, not retrofit on existing roofs as the weight is so great that conventional, existing roofs could not safely carry the added load.
Such a multi-layer system typically consists, in order from bottom to top, of: a waterproof membrane laid over the roof structure top surface; a drainage layer; a root guard layer; a water retention layer; and a growth medium rooting layer on the order of from about 6″ to about 18″ deep, which supports a top layer of rooting vegetation. They may include additional layers or support structures of netting, trays or internal baffles to retain a growth medium on a sloped surface. Thus the typical currently available systems are either site constructed or pre-manufactured to provide a layer of soil on the roof which is then planted on site, or provided with a pre-cultivated vegetative layer. Current technology of both site-built and planted and tray-type pre-cultivated systems are complex, heavy, expensive, and cannot be installed on steep or vertical surfaces.
Examples of other mat systems are shown in the prior art, including Behrens U.S. Pat. No. 5,724,766 directed to use of a thick bat of rock wool as a growth medium for soil-based, rooting plants, such as grass. Plant roots penetrate the mat as they would soil. Providing nutrients to the root system is difficult in rock wool as it is porous and does not retain water well. Thick bats actually float in water, and can slide off roofs in wet conditions. Actual physical installations of this system have not been reported. Behrens also shows in U.S. Pat. No. 6,739,089, a multi-layer pre-seeded mat of flexible biodegradable material, in which the seeds of rooting plants are evenly distributed. This mat overlies and is stitched to a hygroscopic vegetation carrier layer described as “rock wool”. In U.S. Pat. No. 6,158,168, Behrens discloses that German building codes require vegetative slabs to have resistance to fires, citing standard DIN4102, Part 7. In this Behrens variation, the portion of the vegetative slab that is mounted closest to the burnable surface, roof or wall, is fire-retardant water glass (a silica material). The slab comprises >20% by weight of organic substances, such as cocoa, hemp or flax fibers that are embedded in isocyanate foam binders, and includes embedded vascular plant seeds, sprouts and rhizomes.
Iwabuchi, in JP-2003-061458 (English Abstract) discloses a soil-less roof system comprising moss plus water-soluble paper on a base of palm bark that is watered to grow the moss, and then affixed to a building roof. It is not fire resistant. Hirayama, JP2005151860, English Abstract, discloses a net-like covering to prevent scattering of a layer of plants supported on a water resistant layer. The netting appears to be affixed to a water resistant layer by a jig or clip, and the combined laminate affixed to a roof.
Behrens U.S. Pat. No. 5,608,989 describes a 3-layer structure and the need for a drainage and venting (aeration) layer. His top layer contains 4 Kg/m3 of activated carbon plus micro-organisms to adsorb hazardous elements from the atmosphere. This substrate layer can include “mineral wool, rock wool, and glass fibers”. He also discloses a separation layer, a bottom drainage and venting mat, and a seal layer applied to the roof.
Other prior art examples of living roofs and walls include: Fujita US 2008/0072488 Published Application, (disclosing a multi-layer pre-seeded laminate comprising a water insoluble but tearable sheet that is pierceable by the plant growing tips); Berard (Interface, Inc of Atlanta, Ga.) WIPO Publication WO 02/08540, (disclosing a complex multi-layer structure comprising a root barrier layer of polyethylene sheet adhered to a roof, overlain, from bottom up with the following layers: non-woven poly-olefin drainage layer; ¼″-thick water retention layer 16 comprising a non-woven polyester with cross-linked super-absorbent polymer, called but not identified as SAP; a non-woven fabric impregnated with SAP; and finally a seed support layer of cellulose); Behrens U.S. Pat. No. 6,250,010, (disclosing a structural woven or non-woven material on a synthetic fiber substrate, wherein the non-woven top layer overlaps laterally so that there is a lap segment that rests on the adjacent section lower substrate); Behrens U.S. Pat. No. 7,334,376 (disclosing that wind flow over a roof causes up-ward suction that can peel the vegetative layer structure off the roof, so he provides holes in a lower, non-woven cotton layer, a non-woven polyester layer, and on which a looped polyamide fiber layer is glued with a layer of glue); Behrens U.S. Pat. No. 7,204,057 (disclosing use of electrically conductive filaments in a textile fiber substrate on which plans are grown, the filaments being said to shield building occupants against cell tower radiation); Ko, KR2006000324 (disclosing use of zeolite, perlite, illite, and vermiculite as inert fillers that function as heavy metal purifying agents in a composition for vegetative propagation that also includes cereal bran charcoal, “coir dust”, which is cocoanut husk dust, organic fertilizers and a cracking-prevention agent); Ebara, JP2007195455 (disclosing porous substrate for growing grass comprising recycled waste fiber-reinforced cement board); Miwa, JP2003009668 (disclosing open cell foamed glass as a substrate for growing rooting plants on vertical surfaces); Takahashi, JP2006306645 (disclosing a method of producing a base material for surfacing a wall face or roof for supporting plant growth comprising a slurry of both meltable and un-meltable material, fibers and bubbles are added, the material apparently cast in a form, dried and fired at from 400-1300° C.); Ishikawa, U.S. Pat. No. 6,219,965 (disclosing a 3-layer sheet structure for growing grass turf comprising a base web of woven or knitted cotton, polyester or acrylic material for holding water, a core layer, comprising a 3-D open mesh of synthetic resin fibers loaded with sawdust, etc. disposed on the base and including stitched pile yarns projecting above the core layer as plant protection, and grass seeds are sown into and onto the core layer, the grass roots penetrating that layer); Meyer, DE 19629669 (disclosing a 7-layer structure, including a barrier layer, a support sheet, a substrate, and a layer of plant material layer that roots in a plant fiber layer. Over the plants are placed a coarse mesh jute fabric net, and then on top is a spun bonded web. In an alternate embodiment, a metal mesh (screen) is placed between the support and substrate. The whole multi-layer assembly is stitched together).
Accordingly, there remains an unmet need in the art for a living roof and wall system that is inexpensive, easily installed, easy to propagate, easy to maintain, is light weight and less complex, can be used on steep slopes and vertical surfaces, does not require soil or soil substitutes, does not require extensive watering and drainage systems, may be retrofit on suitable existing roofs since light enough to be borne by the load capacity of in-place conventional roofs, is fire resistant, provides an added layer of roof insulation, and is environmentally “green”.